Some lamps comprise an encapsulated light source mounted by brackets, braces, straps and the like within an outer envelope (bulb). The encapsulated light source may comprise a filament tube or an arc tube, and may be of the “two-ended” type having at least one terminal (or electrode, or lead wire) at each of two opposite ends of the encapsulated light source. The two-ended light source may comprise a filament, which may be enclosed. In the main hereinafter, high intensity discharge (HID) lamps having an arc tube may be described, as exemplary of such lamps having two-ended light sources.
A high-intensity discharge (HID) lamp is a type of electrical lamp having a two-ended encapsulated light source, such as an “arc tube” containing a mixture of gases. The arc tube may be suspended (held in place) by various mechanical elements (such as clips, frames, straps, braces, brackets, etc., which collectively may be referred to as the “mount”) inside a translucent or transparent protective outer envelope (“bulb”). The bulb may be somewhat cylindrical, having a “dome” at one end (which may be referred to as the top end) and a “neck” portion at the other end (which may be referred to as the bottom end). The top end of the bulb is generally sealed (not open). A separate “stem” element may be provided at the open, bottom end of the bulb, sealing the bottom end of the bulb. A “base” may be provided at the bottom end of the bulb, such as for screwing the lamp into a socket for mounting and providing electrical current (from an outside source) to the lamp. Electrical current is provided via the base, via various elements of the mount (and or a “fly wire”) to terminals or electrodes of the arc tube.
The arc tube is typically elongated, having two opposite ends, and has electrodes (or terminals, or lead wires) at its two ends. Electricity is applied to these electrodes to create (start, initiate) and to sustain a plasma (or discharge) in the arc tube. Generally, a higher voltage may be required to start the plasma than to sustain it. There are generally two categories (or types) of HID lamp that will be discussed herein:                (i) “pulse-start”, having only two distinct electrodes, one at each end of the arc tube, and which may use an igniter located in a ballast pod, external to the lamp, to start the lamp (initiate the plasma).        (ii) “probe-start”, which uses an additional electrode in the form of a starting probe (or “starter wire”, or “starter lead”) at one of the ends of the arc tube (typically at the bottom end) to facilitate starting the lamp. A simple starting (or starter) circuit such as comprising an inductor and a bimetallic switch may be located within the bulb for initiating the plasma in the arc tube, and the proximity of the starter wire to the electrode at the same end of the arc tube facilitates initiating the plasma. Once the plasma is started, heat generated by the arc tube may cause a bimetallic switch in the starter circuit to open, thereby terminating flow of electric current through the starter wire.)        
FIG. 1 illustrates the construction of an exemplary HID (High intensity Discharge) lamp 100 of the prior art. The lamp 100 is illustrated in a generally vertical orientation, or “base-down”, although it may be inverted or held horizontal in use (such as for overhead lighting applications). In some of the descriptions set forth herein, terms such as “top” and “bottom” may be used to describe the location or position of various elements, such as relative to other elements, and should be evident from the drawings. Other terms such as “left” and “right”, or “front” and “back” may also be used to indicate relative positions of elements as viewed in a referenced drawing figure.
A generally cylindrical arc tube 110 (or capsule) has two end portions 110a and 110b, a central (“chamber”) portion 110c between the end portions 110a and 110b, a length and diameter, and contains one or more gases which, when excited by an appropriate electrical current arcing through the gases, produce light. The end portions 110a and 110b of the arc tube 110 may be flattened (“pinched”) to seal around one or more electrical conductors passing therethrough, and may be referred to as “pinches”. The central portion 110c remains generally cylindrical, and is hollow to contain the gas(es) in a closed chamber.
As is known in the lamp-making arts, other light sources are provided in similarly fashioned capsules which may also be similarly mounted in an outer envelope—for example high pressure halogen atmospheres are contained along with an incandescent filament in a capsule that may be called a filament tube. Therefore, although the present disclosure is focused on an arc tube embodiment of an encapsulated light source, that should be treated as an exemplary embodiment of an encapsulated light source which may be held in a mount structure according to the present invention, as will be disclosed hereinbelow.
At both the top and bottom ends (not specifically labeled) of the arc tube 110, a lead wire (or electrode) extends from external to the arc tube 110, through the respective pinch 110a and 110b, to the interior 110c of the arc tube. The portion of the lead wire external to the arc tube 110 may be referred to specifically as a “lead wire”, and the portion of the lead wire internal to the arc tube 110 may be referred to specifically as the “electrode”. (A similar, additional separate “starter lead” or “probe lead” may also be provided at one end of the arc tube 110, as described below, for probe-start type HID lamps.)
The arc tube may have a band of white coating surrounding the electrodes on one, or both, ends of the arc tube. The coating reflects the heat from the arc and electrode back into the bottom of the end-chamber where the chemicals settle when the arc tube cools. This additional heat helps to vaporize the chemicals into a gas so that they will enter into the arc stream. The vaporized chemicals fuel the arc making it very strong and brilliant. The white coating material may stay white through the lamp life, maintaining optimum end-chamber temperature and resulting in superior lumen maintenance and color consistency.
The arc tube lead wires may be provided in the form of U-pins (U-shaped elements). Generally, any “U-shaped” element may be described as having two “side” or “leg” portions (or simply “legs”, or “sides”) extending substantially parallel (and coplanar) with one another and joined at a common end to each other by a “bow” (or “bend”, or “bight”) portion (or simply “bow”, “bend” or “bight”).
A U-pin 112 is shown extending into the top pinch 110a of the arc tube 110. A U-pin 114 is shown extending into the bottom pinch 110b of the arc tube 110. The bight portions of the U-pins 112 and 114, including a portion of their respective leg portions (or sides), are external to the arc tube 110, and serve as lead wires. Remaining portions of the legs of the U-pins 112 and 114 extend into the respective pinch 110a and 110b, where they are welded to a thin metal foil which is sealed in the pinch. On the interior side of the pinch, an electrode wire/shank is also welded to one of the foils and extends into the interior of the arc tube, to serve as electrodes, in contact with gas(es) contained in the central portion 110c of the arc tube 110. The U-pins 112 and 114 may be formed of wire, such as approximately 0.6 mm (0.020 inch) diameter molybdenum wire.
The U-pins 112 and 114 may also serve a mechanical function. Generally, the U-pin construction with two legs embedded in the pinch of the arc tube may provide a sturdier mechanical interface with the arc tube than would otherwise be realized if only a single pin (lead wire) were to be embedded in the pinch.
The U-pins 112 and 114 also serve as terminals, or electrodes, for providing electrical current to the gases inside the arc tube to initiate and sustain the plasma discharge. For a pulse start lamp, each U-pin connects to one of the two electrodes at opposite ends of the of the arc tube. For a probe start lamp, one of the U-pins, such as the bottom U-pin 114 may be cut (or clipped, such as in half, at the bight) so that one leg of the U-pin constitutes an electrode lead wire (as before), and the other leg is connected to a “starter” or “probe” wire for starting the discharge in the arc tube. This may be referenced as a probe lead wire. Details of a cut bottom U-pin will be shown and described below (FIG. 3B).
In a finished lamp, a protective outer envelope (bulb) 120 surrounds the arc tube 110 which is located and supported more-or-less centrally within the bulb 120 by a “mount structure” 130 comprising various metal wires, frames, bands and straps, as may be described in greater detail hereinbelow. Mechanical and/or electrical connections or attachments of metal components one to another is typically accomplished by welding, but other connection means are possible, therefore the term “welded” should be considered as including other suitable and comparable attachment means within its scope.
The bulb 120 is elongate, somewhat “pear shaped”, having an overall length “L”, is initially open at one end (the bottom end), and has three main portions. A top end portion of the bulb 120 may be referred to as a “dome” portion 122 of the bulb 120. The dome portion 122 may constitute approximately 10% of the overall length “L” of the bulb 120, and is closed. An opposite, bottom end portion of the bulb 120 may be referred to as a “neck” portion 124 of the bulb 120. The neck portion 124 may constitute approximately 20% of the overall length “L” of the bulb, and is initially open (but will be sealed with the “stem”, described hereinbelow). Both of the neck and dome portions 122 and 124 are generally cylindrical, each having a diameter of approximately “D1”. A central portion 126 (or “bulb portion”) of the bulb 120 is disposed between the neck and dome portions 122 and 124. The central portion 126 may constitute approximately 70% of the overall length “L” of the bulb 120, and may have a diameter “D2” greater than “D1”, which gives the bulb 120 its characteristic “pear shaped” (bulbous) appearance. For example, “D2” may be approximately twice as large as “D1” (D2˜=2*D1), and “L” may be approximately twice as large as “D2” (L˜=2*D2). The length “x” of the arc tube 110 may be approximately 60% of the overall length “L” of the bulb 120, and the diameter “d” of the arc tube 110 may be approximately 50% of the smaller (neck, dome) diameter “D1” of the bulb 110. As an example, the overall length “L” of the bulb may be approximately 30 cm (12 inches). In other examples, the bulb length may range between 21-38.5 cm.
A mount structure 130 supports the arc tube 110 within the bulb 120, and also delivers electrical current from the base of the lamp (described below) to the lead wires (essentially, the U-pins 112 and 114, or portions thereof) for the electrodes of the arc tube 110.
The mount structure 130 includes a “top” U-shaped frame 132 disposed in the bulb 120 and extending from within the dome portion 122 into the central portion 126 and a similar “bottom” U-shaped frame 134 disposed in the bulb 120 and extending from within the neck portion 124 into the central portion 126. The top and bottom frames 132 and 134 may be considered to be two parts of a discontinuous two-part frame. The top and bottom frames 132 and 134 may be formed of wire (and may be referred to as “wire frames”), such as approximately 1.6 mm (0.060 inch) diameter stainless steel rod material.
The top U-shaped frame 132 comprises two legs portions (or sides) 132a and 132b extending parallel with one another and joined at one end by a bow (or bend, or bight) portion 132c. Similarly, the bottom U-shaped frame 134 comprises two legs portions (or sides) 134a and 134b extending parallel with one another and joined at one end by a bow (or bend, or bight) portion 134c. The top and bottom frames 132 and 134 may be substantially coplanar with one another, and may be substantially coplanar with the U-pins 112 and 114. The U-shaped frames 132 and 134 are larger than the U-shaped U-pin elements 112 and 114.
The two legs 132a and 132b of the top frame 132 may extend longitudinally downward, slightly beyond the top pinch end 110a of the arc tube 110, generally parallel to the axis of the (cylindrical) arc tube 110, and spaced a small (radial) distance away from (adjacent to) the arc tube 110—in other words, extending adjacent the arc tube 110 adjacent opposite sides thereof. A pair of metal pinch straps (or braces) 142a and 142b (which may collectively be referred to as “142”) extend across the top pinch 110a (on opposite sides thereof), from leg-to-leg of the top frame, and may be fixed (such as by welding) to the two legs 132a and 132b of the top frame 132, thereby securing a top portion of the arc tube 110 in the mount structure 130.
In a similar manner, the two legs 134a and 134b of the bottom frame 134 may extend longitudinally upward, slightly beyond the bottom pinch end 110b of the arc tube 110, generally parallel to the axis of the (cylindrical) arc tube 110, and spaced a small (radial) distance away from (adjacent to) opposite sides of the arc tube 110. A pair of metal pinch straps (or braces) 144a and 144b (which may collectively be referred to as “144”) extend across the bottom pinch 110b (on opposite sides thereof), from leg-to-leg of the bottom frame 134, and may be fixed (such as by welding) to the two legs 134a and 134b of the bottom frame 134, thereby securing a bottom portion of the arc tube 110 in the mount structure 130.
A person of ordinary skill in the related lamp-making and design arts will understand that the references herein to a “pinch strap” (in the singular) is intended to encompass various forms such as, for example, a single ribbon of strapping metal that is wrapped around the pinch; and such as, for example, a pair of ribbons that sandwich the pinch and are attached together (in various ways, e.g., welding) at the two sides of the pinch.
As illustrated, the legs of the top and bottom frames 132 and 134 extend towards each other, and may extend at least to (and possibly slightly beyond) the respective pinches 110a and 110b of the arc tube 110. The leg 132a of the top frame 132 may be in line with the leg 134a of the bottom frame 134, and the leg 134b of the top frame 134 may be in line with the leg 134b of the bottom frame 134. However, the top and bottom frames 132 and 134 are physically and electrically separated from one another, and neither extends longitudinally to adjacent the central portion 110c the arc tube 110. It is generally not desirable that any portion of the mount structure 130 be located adjacent the central portion 110c of the arc tube. (A “fly wire”, described hereinbelow, may pass by the central portion 110c of the arc tube 110, at a suitable distance therefrom.)
A pair of top frame braces (or “supports”) 136a, 136b (which may collectively be referred to as “136”) are disposed in the dome portion 122 of the bulb 120 to support the top wire frame 132. The braces (supports) 136 may each may comprise an elongated metal strip having a length of approximately “D1” and may extend at right angles with respect to a plane defined by the top wire frame 132. One brace 136a may be fixed (such as by a weld) to one of the legs (or sides) of the wire frame 132, at a longitudinal position near the bight end of the top wire frame 132. The other brace 136b may similarly be fixed (such as by a weld) to the other leg (or side) of the wire frame 132, at a longitudinal position near its bight end. The ends of the frame braces 136a and 136b may be slightly bent and/or dimpled, so as to be “snugly” received within the dome portion 122 of the bulb 120 to stabilize the top frame 132 in the dome portion 122 of the bulb 120. The top frame braces 136a and 136b serve a mechanical function, and may be formed of sheet metal, such as 0.5 mm (0.020 inch) thick spring steel material.
U.S. Pat. No. 4,990,819, incorporated by reference herein, discloses a HID lamp having a canted arc tube with rotary locking joints, and discloses what appears to be a set of frame braces (not numbered) similar to the braces 136a and 136b in the dome portion of the bulb and a set of similar looking bottom frame braces (also not numbered) in the neck portion of the bulb.
Referring again to the prior art shown in FIG. 1, a metal strap or wire 152 may extend between the leg 132b of the top frame 132 to a leg of the top U-pin 112, for conducting electrical current from the frame 132 to the arc tube 110. A metal strap or wire 154 may extend between the leg 134b of the bottom frame 134 to a leg of the bottom U-pin 114, for conducting electrical current from the frame 134 to the arc tube 110. This is representative of a pulse-start type HID lamp.
A stem component 160 may be formed of glass (or the like), and may have a diameter approximately equal to the diameter “d” of the arc tube 110, which is less than the diameter “D1” of the neck portion 124 of the bulb. Two stem leads 162 and 164 protrude from the top of the stem component 160. A base component 166, such as a conventional screw-type base (for screwing the lamp into a socket) is disposed around a bottom part of the stem component 160. Leads (not shown) within and exiting the bottom of the stem component 160 electrically connect the stem leads 162 and 164 to the base component 166.
The base component essentially comprises a shell (formed with screw threads), a ceramic insulator, and an eyelet (or button) extending from the bottom. The shell may be nickel-plated brass. The shell and the eyelet constitute what may be considered to be two “terminals” for the overall device (i.e., the lamp).
The bight portion 134c of the bottom frame 134 may be fixed (such as welded) to the stem lead 164. This provides support for the bottom frame 134, hence the arc tube 110, and the top frame 132 attached thereto. Also, the connection of the bottom frame 134 to the stem lead 164 provides electrical current from the base component 166, via the bottom frame 134, via the bottom strap (wire) 154, via the U-pin 114 to the arc tube 110.
A “fly wire” 158 may extend from the other stem lead 162 to a leg 132b of the top frame 132 to provide electrical current from the base component 166, via the top frame 132, via the top strap (wire) 152 via the U-pin 112 to the arc tube 110. The example set forth herein is representative of a pulse-start type HID lamp. For a probe-start type HID lamp, a starting circuit (not shown) may be located in the neck portion 124 of the bulb 120, near the stem component 160, and a separate probe lead would be provided, as is known, and as is described hereinbelow.
U.S. Pat. No. 3,623,134, incorporated by reference herein, illustrates a lamp having a unitary (one-piece), generally rectangular frame, rather then the two-piece frame comprising separate top and bottom frame elements 132 and 134, as disclosed herein. Generally, a unitary frame would be more rugged, but there are disadvantages to having a portion of the frame located abreast of the central portion 110c of the arc tube 110.
FIGS. 1A and 1B illustrate the lamp 100 with the arc tube 110 supported in the bulb 120 between the separate (rather than unitary) top and bottom frame elements 132 and 134, the pinch straps 142 and 144 on respective pinches 110a and 110b of the arc tube 110, the stem component 160, the stem leads 162 and 164, and the base component 166. The fly wire 168 from the stem lead 162 to the top frame 132 is omitted, for illustrative clarity, and since it does not form part of the mount structure (130) per se.
In FIG. 1A, the top and bottom frames 132 and 134 are aligned with one another. Since the top and bottom frames 132 and 134 are not a unitary structure (compare the one-piece rectangular frame in U.S. Pat. No. 3,623,134), this allows for some distortion, bending, pivoting, misalignment and/or breakage of welds, stem, or arc tube pinches when the lamp is subjected to vibration and/or mechanical shock. The articulated frame arrangement in U.S. Pat. No. 4,990,819 may address and alleviate such problems, albeit with added complexity.
In FIG. 1B, the top and bottom frames are shown misaligned, such as may result from vibration or mechanical shock. Such misalignment can lead to failure of welds and/or cracking (not shown) of the glass stem 160, ultimately in failure of the lamp 100. Note the severe misalignment where the top and bottom frames 132 and 134 are welded to the top and bottom pinch straps 132 and 134, respectively. Resulting stress is likely to result in breakage of the welds, and consequent failure of the lamp 100. Also likely to happen is a broken weld of the bottom frame 134 to the stem lead 164. These problems can result not only in mechanical failure, but also the breaking of these welds may interrupt the flow of electrical current to the arc tube (light source) 110.
It is an object of the present invention to provide an improved mount structure and method of mounting for encapsulated light sources such as are in HID lamps (or the like), particularly those having separate top and bottom frames, the improvements making the lamp more rugged (or ruggedized) by improving shock and vibration resistance, and reducing some opportunities for lamp failure.